Posted
by
kdawsonon Sunday March 11, 2007 @02:11PM
from the dwarf-schwmarf dept.

pease1 writes "Wired and others are reporting that for New Mexico, the fight for Pluto is not over. Seven months after the International Astronomical Union downgraded the distant heavenly body to a 'dwarf planet,' a state representative in New Mexico aims to give the snubbed world back some of its respect. State lawmakers will vote Tuesday on a bill that proposes that 'as Pluto passes overhead through New Mexico's excellent night skies, it be declared a planet.' The lawmaker who introduced the measure represents the county in which Clyde Tombaugh, Pluto's discoverer, was born. For many of us old timers, and those who had the honor of meeting Clyde, this just causes a belly laugh and is pure fun. Not to mention a bit of poking a stick in the eye."

Actually, it's still considered a vegetable when talking about tarriffs. The Supreme Court Case Nix v. Hedden [wikipedia.org] decided that and has never been overruled; according to Westlaw (can't link to you since it's a paid service), it's still good law.

Here are a few summary pieces from the Westlaw headnotes:

Tomatoes are vegetables, rather than fruits, in the common and popular acceptation of such words, and were not free of duty under the provision of the free list for fruits, green, ripe, or dried, but were dutiable at 10 per cent. ad valorem, under the provision in Schedule G of the tariff act of March 3, 1883, 22 Stat. 503, for vegetables in their natural state.

It's a pretty ridiculous ruling, as the court says things like this:

The passages cited from the dictionaries define the word fruit as the seed of plaints, or that part of plaints which contains the seed, and especially the juicy, pulpy products of certain plants, covering and containing the seed. These definitions have no tendency to show that tomatoes are fruit, as distinguished from vegetables, in common speech, or within the meaning of the tariff act.

My favorite part is the justification about how the people think it's a vegetable because of when they eat it:

in the common language of the people, whether sellers or consumers of provisions, all these are vegetables which are grown in kitchen gardens, and which, whether eaten cooked or raw, are, like potatoes, carrots, parsnips, turnips, beets, cauliflower, cabbage, celery, and lettuce, usually served at dinner in, with, or after the soup, fish, or meats which constitute the principal part of the repast, and not, like fruits generally, as dessert

I might add that this reasoning doesn't work anymore, since a lot of people consume fruits with their meal (orange juice, strawberries in cereal, bananas in packed lunches, canned peaches, etc.).

The court then goes on to talk about beans, and how they are used as vegetables even though they are not vegetables. I have to wonder what the court would have thought of the sweet bean, which is eaten as a dessert in Japan. Would they have ruled that this bean is a fruit?

This is what happens when a poorly thought definition change occurs. The dynamics of the Pluto orbit were known for a long time. There's been no sudden increase in scientific insight due to this capricious change. Let's look at the facts. Pluto was considered a planet for more than 75 years. In recent times, many Kuiper Belt objects (which by definition interact gravitationally with Neptune) were found, one which is probably even larger [wikipedia.org] than Pluto and at it's closest approach can be closer to the Sun than Pluto is at it's most distant. There may be many such objects larger than Pluto. So yes, if Pluto were discovered now (ignoring the new definition), it probably would not be considered a planet.

But let's look at the definition. Pluto satisfies the first two conditions, it is in orbit around the Sun and is massive enough to form a sphere. The third condition is that "it must have cleared the neighbourhood around its orbit". That phrase has yet to be defined. So we're saying Pluto is not a planet even though we don't yet know the meaning of a critical term. Let me point out what should be obvious. Namely, if one defines the neighborhood of an orbit as a locus of the trajectory (in four dimensional space-time, eg, the space within distance d of the object at time t), then anything big enough to be round most likely has cleared an impressively large neighborhood of anything of similar mass. I assume reasonably that "cleared" means here that no amount of mass similar in order of magnitude routinely runs through this neighborhood. Also, it ignores the grief that the definition change causes to the outside world. Science textbooks need to be modified to reflect this new definition. Given that the definition is "official" yet is still mostly incomplete, the IAU will need to complete the definition of planet (and you can bet that Pluto == planet is still on the agenda). Finally, the definition explicitly only defines "planet" in the Solar System. The related definition of "dwarf planet" (ie, if it is massive enough to be rounded by gravity, it's a dwarf planet) does apply to exosolar dwarf planets (by a 2003 decision by the IAU).

So all this effort fails to apply to other star systems. This is quite relevant. First, the Solar System is a mature star system, more than 4 billion years old with no signs of recent perturbation. Second, all the orbits of the "planets" are circular. That's unusual. Most of the objects yet discovered have very elliptical (ie, large eccentricity) orbits. The definition would be hard to observe anyway since one would need to be able to account for most of the nonstellar mass in the star system before they could claim that anything has "cleared its orbit".

Finally, the decision was made with little concensus. The IAU is not an open-membership body. My impression is that it admits members directly by election only or at the behest of a "national member", a national level organization (like the US National Academy of Science's Board on International Scientific Organizations [nationalacademies.org]) which may have similar membership requirements. IMHO, IAU membership isn't constituted in a way conducive to concensus outside the astronomy community. Second, as noted before, only 5% of the members of the IAU actually voted on the definition in question. Further, only IAU officials had the power [space.com] to modify the definition when it was being voted on. Finally, no report of the actual vote has ever been made public, as far as I can tell. We know that 424 members voted on it (this is widely reported in the media), but I have never seen reported the actual vote tally.

In summary, a redefinition of a common term, "planet" which manages to remain ill-defined and to have little scientific value by an international body that failed to generate any concensus either inside or out on the decision.